P. W. Anderson showed that this property is robust against imperfections in “dirty” materials displaying this property. Electrons in materials displaying this property pull positive charge carriers towards them, resulting in a small attractive force on other electrons. Within these materials, the magnetic field obeys a Helmholtz equation with eigenvalue equal to one over the square (-5[1])of the (*) London penetration depth. (10[1])1.764 times the Boltzmann constant times the critical temperature for this phenomenon gives (10[1])the energy gained by forming a Cooper pair in the BCS theory of (10[1])this phenomenon. (10[1])For 10 points, name this low temperature phenomenon in which a material’s DC electrical resistance drops to zero. ■END■